The present invention generally relates to breast tumor screening devices and methods and, more particularly, is concerned with an in situ tumor temperature profile measuring probe and a method of using the probe.
The early detection of tumors, which is the principal strategy for reducing the mortality of breast cancer, is a challenging task. X-ray mammograms, widely used for mass screening, cannot reliably detect early tumors much below 1 cm in size. The false negative rate is 5 to 15% for tumors of palpable size. Mammography is inconclusive in differentiating malignant tumors from nonmalignant breast disease, such as harmless cysts and benign fibroid tissue. Ultrasound, which is commonly used to discriminate between tumor masses and cysts after indications are found with mammography, does not have the sensitivity to detect very small invasive tumors. Magnetic resonance (MR) imaging lacks sensitivity and specificity. With MR dynamic contrast methods, sensitivity is high but the specificity is not high enough to reliably resolve benign from cancerous lesions. Histo-pathological findings from biopsies are the only reliable means of breast cancer diagnosis and, consequently, many women are subjected to biopsies to improve their chances for long-term survival if any abnormality is found.
Angiogenesis is the growth of new blood vessels from existing capillaries. It is a fundamental process of tumor growth and metastasis. All solid tumors require angiogenesis for growth. This process has received much attention since it was first postulated in 1971. In breast cancer, it has been shown that the level of angiogenesis as defined by microvessel density has prognostic value. Studies have shown that the levels of angiogenesis in breast cancer are correlated with the potential for metastasis and aggressive growth. The angiogenic switch occurs early in tumor growth. A method that is sensitive to increased blood perfusion in a suspected lesion would be of value for early detection of breast cancer.
Tumors have a higher temperature than surrounding tissue by virtue of increased blood circulation in the tumor, particularly in the peripheral region of the tumor. Increased perfusion of arterial blood could set up a temperature gradient from the tumor interior to the surrounding tissue. It is believed that excess tumor temperature could also arise from the higher metabolic rates of growing tumor cells. This temperature excess has been visualized by surface thermography in the case of large tumors near the surface of the breast, though surface infrared thermography in clinical practice became controversial for a number of technical reasons.
It appears that no reliable or accepted data are available on the characteristics of tumor temperatures by other imaging methods or by in situ methods. In the former case, magnetic resonance (MR) imaging cannot produce an ab initio temperature map of tissue due to the variations of phase or frequency caused by variations in susceptibility of tissue. In the latter case, single-point temperature measurements are subject to considerable error due to heat conduction effects of the sensor itself and of unknown temperature gradients in the tissue. In situ probes for internal temperature must satisfy rigorous requirements on conduction of heat and thermal mass and must be capable of sensing small temperature gradients reliably. Tumor temperatures can only be inferred from non-invasive surface thermography images and, thus, are limited in sensitivity, resolution and accuracy.
Because current imaging modalities cannot completely identify all cancerous lesions, many biopsy procedures are performed. Surgical biopsy procedures are particularly expensive and uncomfortable to patients. The lesion is visualized and a localizing guide wire is placed through a small needle into the lesion. The needle is removed. The guide wire is left in place. The patient is taken to surgery for the surgical biopsy procedure in which the wire localizes the lesion center for the surgeons. A reduction of such procedures would be desirable. Other common biopsy procedures for the breast involve less invasive needle methods with vacuum aspiration.
The inventors herein have recognized the desirability of having a temperature probe that could be used to provide added information to radiologists and which would be helpful in avoiding more severe forms of biopsy procedures. However, problems exist with current temperature probes which are found in the prior art. Current temperature probes are relatively large. The smallest conventional thermocouple wires are about 120 micrometers in diameter and are very fragile. Two such wires are needed for each probe element. The thermal conductivity of the wires in these relatively large probes affects the temperature measurements made by the probe with the result being that the probe does not measure tumor temperatures with high accuracy.
Consequently, a need remains for a tumor temperature probe which is smaller in size than prior art probes and can provide reliable and sensitive temperature measurements and thus would overcome the aforementioned problems of the prior art probes, without introducing any new problems in place thereof
The present invention provides an in situ breast tumor temperature profile measuring probe and a method of using the probe which are designed to satisfy the aforementioned need. The in situ tumor temperature profile measuring probe of the present invention is relatively small in size and does not produce a level of thermal conductivity that would affect the temperature measurements made by the measuring probe. The measuring probe has an array of temperature sensors, being microscopic in size, that will be able to detect and thus provide a profile of temperatures of a breast tumor and surrounding tissue with high accuracy. The measuring probe may be used with standard breast biopsy procedures and is capable of measuring small temperature differences in and around breast tumors so as to enable the diagnosis of cancer at an early stage when the tumor is small in size. The measuring probe thus will fulfill the need for a suitable temperature probe which would provide added information to radiologists and may be helpful in avoiding more severe forms of biopsy procedures.
In one embodiment of the present invention, an in situ tumor temperature profile measuring probe is provided which comprises: an elongated rod including a pair of opposite end portions, an outer insulating layer having a plurality of spaced apart holes defined therein at one of the opposite end portions of the rod, and a common electrical input lead extending between the opposite end portions of the rod and disposed below the holes and having portions exposed at the holes, the common electrical input lead being adapted to provide an electrical input signal; a plurality of spaced apart thermal sensors each formed within one of the holes of and on the outer insulating layer of the rod in electrical contact with the common electrical input lead of the rod, each thermal sensor being adapted to receive the electrical input signal from the common electrical input lead, sense the temperature of biological matter adjacent to where the thermal sensor is placed and produce an electrical output signal correlated to the temperature sensed; and a plurality of electrical output leads each mounted to the outer insulating layer of the rod in electrical contact with a different one of the thermal sensors and extending to the other of the opposite end portions of the rod, each of the electrical output leads being adapted to receive the electrical output signal from the one of the thermal sensors and output the electrical output signal to means for collecting the output signals and forming a temperature profile of the biological matter.
More particularly, the common electrical input lead of the rod is either a hollow tube or an elongated strip, each made of an electrically conductive material. The holes and thermal sensors therein are arranged in either a linear array in which the thermal sensors are aligned axially with one another along the rod or a staggered array in which the thermal sensors are offset circumferentially and axially from one another about and along the rod. Each thermal sensor and each electrical output lead are microscopic, or micron-scale, in size. The probe further comprises an exterior insulating layer covering at least the electrical output leads.
In another exemplary embodiment of the present invention, an in situ tumor temperature profile measuring probe assembly is provided which comprises: the above-defined measuring probe; a hollow needle being insertable-into biological matter and having opposite ends and an interior passageway defined through the hollow needle which are open at each of the opposite ends thereof so as to adapt the hollow needle to receive the measuring probe through the interior passageway and guide the one end portion of the measuring probe into the biological matter; and an electrical connector for providing an interface between the electrical input and output leads of the measuring probe and a computer, the connector being adapted to receive the electrical output signals from the electrical output leads of the measuring probe and transmit the temperatures sensed by the thermal sensors of the measuring probe to the computer for collecting the output signals and forming a temperature profile of the biological matter.
In a further exemplary embodiment of the present invention, a method of measuring an in situ tumor temperature profile is provided which comprises the steps of: providing a common electrical input signal; receiving the common electrical input signal at spaced apart locations within biological matter; sensing temperatures of the biological matter at the spaced apart locations within the biological matter; producing a plurality of electrical output signals corresponding to the respective temperatures sensed; and transmitting the electrical output signals produced to a computer for collecting the output signals. The method also comprises the steps of forming a temperature profile of the biological matter and using the temperature profile of the biological matter to determine whether a tumor is present and what type of a tumor may exist in the biological matter.